Precision dental paralleling process



Feb. 1, 1966 w, HARRls 3,231,977

PRECISION DENTAL PARALLELING PRQCESS Filed March 23, 1964 2 Sheets-Sheet 1 Pica-E INVENTOR W/LL/AM H, HARP/5 Feb. 1, 1966 w, HARRIS 3,231,977

PRECISION DENTAL PARALLELING PROCESS Filed March 23, 1964 2 Sheets-Sheet 2 INVEN TOR. I V/ZL [AM H. HARP/'5 United States Patent 3,231,977 PRECISION DENTAL PARALLELING PROCESS William H. Harris, 4601 S. Pennsylvania, Oklahoma City, Okla. Filed Mar. 23, 1964, Ser. No. 353,943 7 Claims. (Cl. 32-67) This invention relates to a process for drilling holes in precise parallelism in one or a plurality of teeth while said teeth are in their natural position in the mouth. More particularly, the present invention relates to a method for improving the ease and accuracy with which holes may be drilled in a precise location in a dentition and, in a preferred embodiment of the invention, comprises a multi-step procedure for drilling at least two holes in substantially perfect parallelism in one or more teeth while the teeth are in their natural locus in the mouth of a patient. In another of its aspects, the invention relates to an instrument which may be used in practicing the process of the invention.

It has for some time been recognized in dentistry that, for the purpose of anchoring bridges, crowns and inlays in their proper positions in the mouth of a patient, a more secure hold or adhesion to the tooth may be obtained by the use of parallel pins affixed to the bridge, crown or inlay and projecting into parallel canals or holes drilled in the teeth than can be obtained when a so-called three-quarter type crown or bridge is used to secure the dental castings in place. When it is attempted to secure fixed crowns in place using the three-quarter crown structure, masticatory stresses result in fatigue of the gold used in constructing such dental castings, and the formation of a space occurs between the tooth surface and the gold. The crown or bridgework then becomes loose and is difficult to retain in place over the teeth. In other words, except when parallel pins cooperating with matching holes formed in the teeth are used conjunctively with the frictional grip of the gold around the tooth to retain the bridge or crown in place, the dental casting is easily lost due to its dependence solely upon the mechanical strength of the gold alloy for retaining it in position. With pin retention of the type described, the crown or bridge is locked in the tooth so that the masticatory stresses are unable to result in any fatigue of the gold.

The pin type of anchorage for incisors and cuspids has been known in the dental profession under the name of pinledge for nearly fifty years, but has been very little used, and for bicuspids and molars, hardly at all. This has probably been due mainly to the fact that, with the methods heretofore practiced, the technique puts too great demands on the technical knowledge and skill of the average dentist.

One of the most diflicult aspects of providing holes in the teeth for the purpose of affording anchorage for cast gold restorations, such as bridgework, crown and inlays, is the necessity that such holes be precisely parallel with each other in order to permit the pins which project from the cast gold restoration to move easily into the holes without interference by the teeth. The difliculties of guiding and aligning the drill which is used to form the holes in the teeth as a plurality of holes are formed in separate teeth are particularly great as a result of the necessity to operate within the limited area afforded by the mouth of a patient. A number of very complicated paralleling devices have heretofore been contrived which assure that the drill, as it is brought into contact with the teeth a plurality of times will, in each instance, be retained in parallelism with its former position. However, many of these devices include a number of moving parts which must somehow be made compactly enough to be placed in the mouth'of'a patient, and the'result'is either a sacrifice of precision or a complicated instrument of such size that its placement in the patients mouth results in severe discomfort to the patient and the necessity to remove the instrument from the patients mouth periodically to permit a period of rest.

It will further be apparent that, even though instruments may be provided for assuring that the drill used in attempting to drill parallel holes in the teeth is moved during all of its movements in planes which are parallel to each other, the slightest movement of the patients head will result in failure of the holes to be maintained in parallelism as they are drilled.

Another extremely serious problem which has characterized the technique of drilling parallel holes in the teeth, as this procedure has been previously practiced in dentistry, is that of being assured that the holes, though precisely parallel with each other, are drilled into portions of the tooth which do not seriously damage the tooth, such as into the pulp cavity. The dentist will gen erally estimate the best position for drilling the hole based upon X-rays of the teeth which have been previously taken. However, whether or not the hole is formed in the teeth at the precise location desired will again be dependent upon the degree of precision with which the dentist may retain the teeth in the same position as the drill is moved from one tooth to the next, and also the steadiness with which the paralleling apparatus is maintained in its initial position.

The present invention provides a novel procedure for drilling holes in perfect parallelism in one or a plurality of teeth while the teeth are retained in the natural position in the mouth of a patient. The method may also be used to drill a single hole in the teeth of the patient if such should be desired, but the primary benefit of the method resides in its ability to assure that the holes are drilled in the precise spot in the teeth where desired, and that a plurality of holes may be drilled in the teeth in absolute and perfect parallelism. A minimum of discomfort to the patient is entailed in the technique, and the apparatus which is utilized in the method is very simple, inexpensive, and is quite easy to utilize.

Broadly, the process of the present invention may be described as comprising the steps of forming a jig which is complementary in configuration to that portion of the teeth in which one or more holes are to be drilled so that the jig conforms in shape to the outline of said teeth and will fit tightly over the teeth, the jig being formed (and, when a plurality of holes are to be formed, retaining in the same position relative to each other) a plurality of elongated, generally tubular guide sleeves extending par allel to each other and positioned in the jig in a position of coaxial alignment with the projected axes of the holes which are to be drilled in the teeth; then fitting the jig over the teeth in the mouth with the generally tubular guide sleeves contacting the teeth at the points where it is desired to drill the holes in the teeth; and finally, passing an elongated drilling tool through each of said elongated, generally tubular guide sleeves and drilling said holes while the drilling tool is guided and aligned by the tubular guide sleeves. In some instances, the technique may be desirably used to drill but a single hole in one tooth. Most frequently, however, the procedure is used for the purpose of permitting a plurality of holes to be formed in the teeth with the axis of the holes being in perfect parallelism so that a series of parallel pins carried by inlays, crowns and bridgework will move easily into the receivir'igiholes without binding or striking against portions of the teeth.

Although the foregoing description is a broad description of the basic steps which constitute the heart of the present invention, a preferred method of practicing such,

process comprises initially making a rigid model of the portion of the teeth in which the holes are to be drilled, with the model being substantially identical in size and configuration to said portion of the teeth; aligning a straight, elongated rigid guide member with a point on the model corresponding to a point on the teeth at which one of the holes is to be drilled with the guide member being aligned with its longitudinal axis coincident with the projected axis of said one hole; placing a first generally tubular guide sleeve over said elongated, rigid guide member so that said first sleeve contacts said model while coaxially aligned with said projected axis; adhering said first tubular guide sleeve to said model while said first tubular guide sleeve is coaxially aligned with said projected axis and in contact with said model; withdrawing said rigid guide member from said first tubular guide sleeve and moving said rigid guide member into contact with said model at a point where a second of said holes is to be drilled, said withdrawal and movement of the rigid guide member being carried out while the guide member is retained in absolute parallelism with its former position (that is, moves constantly in planes which are parallel to each other); placing a second, generally tubular guide sleeve over said elongated rigid guide member so that said second tubular guide sleeve contacts said model at the point on the model corresponding to the point on the teeth of the patient where a second hole is to be drilled, said second, generally tubular guide sleeve having its axis extending parallel to the axis of said first, generally tubular guide sleeve; adhering the second tubular guide sleeve to said model while said second tubular guide sleeve is coaxially aligned with a line corresponding to the projected axis of the second hole to be drilled in the teeth and is aligned in parallelism with said first tubular guide sleeve; forming a jig over the teeth of said model in which said holes are to be drilled and around said first and second tubular guide sleeves, said jig enclosing said first and second tubular guide sleeves with said guide sleeves extending through said jig from one side thereof to the other, and said jig being rigid to retain the precise spacing and orientation of said first and second tubular guide sleeves relative to each other; placing said jig in the mouth of the patient over the teeth in which said holes are to be drilled with the ends of said first and second tubular guide sleeves contacting said teeth at the points where said holes are to be drilled; and finally, extending an elongated drilling tool through said guide sleeves and drilling holes in the teeth of the patient while said drilling tool is guided and aligned by said tubular guide sleeves.

It is believed that it will be apparent from the foregoing description of the process used in the present invention that a major object which is attained by the invention is the drilling of a plurality of holes in precise parallelism in one or more teeth of a patient with a minimum of difliculty and discomfort to the patient.

An additional object of the present invention is to permit a dentist to more easily ascertain the best location for drilling a hole in a tooth, and the best angle at which to drill such hole.

An additional object of the present invention is to provide an improved method for drilling canals or holes in the teeth for the accommodation of pins carried by dental castings, such as bridgework, inlays and crowns.

Yet another object of the present invention is to provide a novel dental paralleling technique which can be carried out with a minimum of difliculty and using apparatus which is relatively inexepnsive and simple in construction.

A further object of the present invention is to permit a dentist of average skill to do a relatively better job of drilling parallel holes in teeth than has heretofore been possible.

Another object of the present invention is to provide a novel instrument for use in the technique of paralleling as practiced in dentistry, said instrument being simple and inexpensive in construction, and being also adapted for use in the technique of dental surveying.

A further object of the present invention is to permit paralleling to be carried out in dentistry with less discomfort to a patient.

In addition to the foregoing described objects of the invention, additional objects and advantages will become apparent as the following detailed description of the invention is read in conjunction with a perusal of the accompanying drawings which illustrate the invention.

In the drawings:

FIGURE 1 is a view in elevation of a preferred embodiment of an instrument useful for spotting in on a model of the teeth, the alignment and position of holes to be drilled in the teeth. The instrument is shown as it is being used to spot the holes to be drilled in the teeth using a model of the teeth of the patient.

FIGURE 2 is an enlarged detail view illustrating the manner in which the instrument portrayed in FIGURE 1 is used to position a generally tubular guide sleeve on the model of the tooth at the position where it is desired to drill a hole in the tooth and with the longitudinal axis of the elongated generally tubular guide sleeve in coaxial alignment with the projected axis of said hole.

FIGURE 3 shows a model of a plurality of teeth in which it is desired to drill holes for the purpose of attaching a bridge, and illustrating four elongated generally tubular guide sleeves and fixed in position on two teeth of the model by the use of a suitable adhesive.

FIGURE 4 is a view in elevation illustrating the manner in which a jig is constructed for removing the generally tubular guide sleeves from the teeth of the model in perfect parallelism and transferring them to a position over the teeth in the patients mouth in which they remain in parallelism.

FIGURE 5 is a view in elevation of the jig with the generally tubular guide sleeves embedded therein after the jig has been transferred to the mouth of the patient and superimposed over the teeth of the patient in which holes are to be drilled. FIGURE 5 also shows a drill extending through one of the tubular guide sleeves for the purpose of drilling a hole in one tooth of the patient.

FIGURE 6 is an enlarged detail view of the upper end of the elongated spotting tool forming a part of the instrument shown in FIGURE 1 and showing the manner in which the upper end of the spotting tool is grooved and bored to receive a marking member.

FIGURE 7 is a detailed view illustrating the manner in which the instrument shown in FIGURE 1 can be used for a dental surveying operation.

Referring now to the drawings in detail, and particularly to FIGURE 1, the method of easily accomplishing the drilling of parallel holes in the teeth of a patient while the teeth are in place in the mouth in accordance with the practice of the present invention will be explained conjunctively with an explanation of the novel instrument which is used in practicing such method. The term dentition when used hereinafter or in the claims of this application refers to one or more teeth in which a plurality of holes are to be drilled. Reference character 10 refers to a horizontal stage which, in a preferred embodiment of the invention, is disc-shaped as would more clearly appear were the stage viewed from above, or at from the angle of view illustrated in FIGURE 1. The horizontal stage slidably supports a small rigid plate 12 of metal or plastic which is freely movable in a horizontal plane while supported on the upper surface of the stage 10.

The plate 12 supports a relatively large mass of a deformable, adherent material 14 which can be easily altered in shape by the pressures which the average person can exert with the fingers. The material of which the deformable mass 14 is formed is preferably sufiiciently tacky to prevent relative slipping between this material and the upper surface of the plate 12. It is also sufiiciently tacky to retain in position on the upper surface, thereof,

a model 16 of the teeth of the patient of the type which dentists customarily make from plaster of Paris or socalled stone. I have found that a very suitable material of construction for the deformable mass 14 is ordinary molding clay of the type used by chlidren for molding various shapes and objects. This molding clay can be easily deformed so as to adjust the angle which the model 16 forms with the horizontal, and thus to change the general plane of the teeth carried by the model. The purpose of this adjustability of positioning will become apparent as a description of the use of the tool shown in FIGURE 1 is further considered.

Extending upwardly from the stage is a rigid, vertical post 18. The post 18 may be positioned at any location on the stage 10, but is preferably adjacent the peripheral edge thereof. The total height of the post 18 is not critical except that it should extend to a considerably higher level than the level of the teeth carried by a model 16 when the model is positioned on the deformable mass 14 in the manner illustrated in FIGURE 1.

A rigid, horizontal arm extends normal to the rigid, vertical post 18 and is slidably and rotat-ably mounted therein by means of a sleeve 22. The bore of the sleeve 22 which receives the post 18 is of sufficient length and is machined sufliciently close in tolerance to the diameter of the post 18 that there can be no significant play which will permit the rigid horizontal arm 20 to depart from parallelism with the stage 10 or its occupancy of a plane extending normal to the post 18. It will be perceived that the rigid horizontal arm 20 may be moved freely in a vertical direction on the vertical rigid post 18, and that this arm may also be pivoted in a horizontal direction about the axis of the post 18. The arm 20 may be fixed in any desired position which it is capable of occupying by turning a set screw 24 so as to engage the rigid vertical post 18 with the inner end of the screw. The set screw 24 is, of course, threaded through the body of the sleeve 22.

At its outer end 26, the rigid, horizontal arm 20 carries a second sleeve 28 which is provided with an elongated bore (not seen) extending therethrough. In a preferred embodiment of the invention, the bore extends vertically and is substantially normal to the arm 20. However, in more expensive embodiments of the invention, the sleeve 28 can be swivelly mounted on the end of the arm 20 for adjustment so that the bore of the sleeve extends at any desired angle with respect to the vertical.

An elongated spotting tool 30 is slidably mounted though the bore in the sleeve 28. The length of the bore through the sleeve 28 and the relatively small clearance between the sleeve and the spotting tool 30 are such that the spotting tool is always maintained at substantially precisely the same angle with respect to both the stage 10 and the rigid, horizontal arm 20 as is the bore through the sleeve 28. Thus, even though the set screw 24 is loosened, and the arm 20 is moved vertically relative to the stage 10 or horizontally about the axis of the vertical post 18, the angle formed by the elongated spotting tool 30 relative to the vertical will always remain the same.

At its lower end, the elongated spotting tool 30 carries a guide member such as a cylindrical spotting mandrel 32 which is of substantially smaller diameter than the general diameter of a molar tooth as may be perceived in referring to FIGURE 1. The diameter of the spotting mandrel 32 is also substantially the same as the diameter of the holes which it is desired to drill in the teeth. As illustrated in FIGURE 1, the spotting tool 30 has been lowered in the sleeve 28 until the lower end of the spotting mandrel 32 has come-in contact with one of the molar teeth 34 of the model 16.

At its upper end, the spotting tool 30 is relieved or cut away to approximately half of its diameter and a groove 36 is formed therein for detachably receiving a marking device, such as a pencil lead 38, as shown in FIGURE 6. The groove 36 is preferably extended into team-t "6 the unreliev-ed portion of the spotting tool 30 where it becomes a small bore extending for a short distance into the spotting tool. The upper end of the spotting tool 30 which carries the groove 36 is used in the procedure of dental surveying as will be hereinafter more specifically described.

In using the instrument illustrated in FIGURE 1 in the process of drilling parallel holes in the teeth while the teeth are in place in the mouth, a plaster of Paris or stone model of the teeth is first formed. This technique is well-known in the dental technology and need not be described here in detail. The model is then placed on the mass of deformable adherent material 14 and is pressed gently down on the material 14 until it adheres to the material. The horizontal and vertical angles of the model 16 are then adjusted, along with concurrent adjustments of the position of the spotting tool 30 and spotting mandrel 32 relative to the teeth of the model so that the lower end or tip of the spotting mandrel 32 touches a particular tooth at the exact point where it is desired to drill a hole therein. It is also possible by comparison of the position of the model 16, the position of the spotting mandrel 32 and X-rays of the teeth to determine whetherthe angle at which the drill will enter the teeth is the angle desired. In other words, as will subsequently become apparent, the angle which the spotting mandrel 32 forms with the model 16 of the teeth corresponds to the angle of attack of the drill as the holes are subsequently drilled in the teeth. Thus, by manipulation of the model 16 so as to place it at a particular angle with respect to the spotting tool 30 and spotting man-drel 32, the dentist can be assured that he will subsequently be drilling holes in the teeth at the exact point and at the exact angle which he desires to drill.

Once the model has been positioned at an angle which affords the proper attack angle of the drill, the adhesive quality of the deformable material 14 will retain the model in this position until the spotting-in operation is completed. Having found the proper angle for drilling the first of the teeth in which a hole is to be drilled, the spotting tool 30 may then be slipped upwardly in the sleeve 28 so as to permit guide means such as a small elongated tubular guide sleeve 38 to be placed over the spotting mandrel 32. The tubular guide sleeve 38 is formed of a hard, metallic material, preferably steel or brass. The clearance between the tubular sleeve 38 and the spotting mandrel 32 is very slight so that the tubular guide sleeve 38 is exactly coaxially aligned with the spotting mandrel.

With the guide sleeve 38 on the spotting mandrel 32, the spotting tool 30 is again moved downwardly in the sleeve 28 until the lower end of the spotting mandrel 32 touches the surface of the tooth at the point where it is desired to drill the hole. Concurrently, the tubular guide sleeve 38 is slid down the cylindrical spotting mandrel 32 until it is also in contact with the surface of the tooth of the model. With the tubular guide sleeve 38 in the described position, a small amount of a liquid adhesive is placed at the base of the tubular guide sleeve 38 where it contacts the model tooth 34 so as to bond the guide sleeve to the tooth and retain it in the identical position illustrated in FIGURE 2 subsequent to the withdrawal of the spotting mandrel 32 from the guide sleeve.

After the first tubular guide sleeve 38 has been spotted in on the first tooth 34 of the model 16 at the point where a first hole is to be drilled in the teeth, the spotting tool 30 is moved upwardly in the sleeve 28 to permit the plate 12, deformable material 14 and model 16 to he slid to a new position under the spotting tool so as to bring the lower end of the spotting mandrel 32 into alignment with a point on a second tooth 35 of the model where it is desired to drill another hole. Independently of the described movement of the model 16, the rigid horizontal arm 20 may be pivoted in ahorizontal plane to assistin bringing the spotting tool 30 into alignment with the next tooth of the model 16 which corresponds to one of the natural teeth in which a hole is to be drilled. Care is execised in the movement of the plate 12 and the model 16 to retain the model in the identical position relative to horizontal and vertical planes which it occupied at the time when the first hole was spotted in in accordance with the procedure hereinbefore described. It will thus be perceived that since the model is maintained in the same orientation relative to a horizontal plane, and since the spotting tool 30 is also maintained at the same angle with respect to vertical and horizontal planes, the spotting mandrel 32 moves in exact parallelism at all times and will contact the next tooth on the model at exactly the same angle as the angle of attack depicted in FIGURE 2.

As the model 16 and spotting tool 30 are repositioned relative to each other so as to permit the spotting mandrel 32 to be brought into contact with the same tooth or other teeth on the model at the points corresponding to the points on the natural teeth where it is desired to drill holes, the procedure of spotting in the tubular guide sleeves 38 on the teeth is repeated, and each of the several guide sleeves 38 are adhered to the surface of their respective teeth in the same manner as has been hereinbefore explained. Thus, in FIGURE 3, the portion of the model 16 is depicted which illustrates a pair of teeth 34 and 35 which correspond to two natural teeth in the patients mouth in which it is desired to drill a total of four holes for the purpose of permitting a bridge to be affixed to the teeth. It may be perceived that the tubular guide sleeves 38 are each precisely parallel to each other. The guide sleeves 38 will be coaxially aligned with the projected axis of holes which would be formed in the teeth of the model if these teeth were the actual nautral teeth of the patient.

The next step in the :process of the invention is the formation of a jig 40 which is used to transfer the tubular guide sleeves 38 while in absolute parallelism from the model 16 to the natural teeth of the patient. The model 16 is first precoated with a releasing compound, the function of which will be subsequently explained. The next step in the formation of the jig 40 constitutes the positioning around the teeth on the model 16 corresponding to the teeth which are to be drilled, an amorphous, moldable material 41 which can be cured or permitted to set up to a hardened state after it is molded around the teeth of the model and the tubular guide sleeves 38. A suitable material which may be used for forming the jig is one of the quick curing impression plastics widely used in the technology of dentistry.

The material 41 is packed and molded around the teeth of the model 16 which correspond to the teeth in which the holes are to be drilled so as to conform exactly to the contours of the teeth and to encase the teeth, and desirably, a portion of the gum, in the material 41. It will further be noted that the tubular guide sleeves 38 are permitted to project through the material 41 so that access to the guide sleeves may be had without obstruction by the jig 40.

After the moldable material 41 has been allowed to set up into a hardened mass, it is removed from the model 16. Removal from the model 16 is accomplished with a minimum of difiiculty as a result of precoating the gum and teeth of the model which are to be contacted by the moldable material 41 with a releasing compound or separatory medium, such as water glass. The latter material reduces the adhesion between the moldable material 41 and the model 16 so that the jig 40 formed by the material may be easily detached from the model. As the jig 40 is detached from the model 16, it carries with it embedded in the moldable material 41, the several tubular guide sleeves 38. The guide sleeves 38 are retained by the rigid jig 40 in the same strict parallel status by which the position of these elements was characterized when 8 they were adhered in position on the teeth of the model 16 as shown in FIGURE 3.

After the jig 40 has been removed from the model 16, it is fitted over the natural teeth of the patient in the patients mouth. Because the jig 40 constitutes a pattern of the teeth and is complementary in configuration to the teeth, it will form a snug fit over the teeth and the tubular guide sleeves 38 will be positioned relative to the natural teeth of the patient in precisely the same manner as they were positioned relative to the model 16 of the patients teeth. Thus, the dentist is assured that the points of contact of the tubular guide sleeves 38 with the teeth will correspond to the points at which it is desired to drill holes in the teeth. Moreover, once the jig is in place in the patients mouth, the axes of the tubular guide sleeves 38 will coincide with projections of the axes of the holes which it is desired to drill in the teeth.

The final step in the practice of the paralleling process of the invention is that of actually drilling holes in the teeth of the patient. The holes are drilled by extending through each of the tubular guide sleeves 38, a suitable drilling device, such as a burr drill or some other suitable type of drill bit 44. The diameters of the drill bit 44 and the tubular guide sleeves 38 are such that there is very little clearance between the bit and each of the guide sleeves. Thus, the bit is not permitted to wobble in the sleeve and is guided by the sleeve along a line of attack which is precisely coincident with the axis of the guide sleeve and with the projection of the axis of the hole which it is desired to drill in the respective tooth. As the drill bit 44 is moved from one guide sleeve 38 to another in drilling a plurality of holes in the teeth, the exact parallelism of the several guide sleeves assures that the holes which are drilled by the drill bit 44 will also be precisely parallel to each other. When the drilling of the holes has been completed, the jig 40 with its embedded tubular guide sleeves 38 may be easily slipped from the teeth and removed from the patients mouth.

From the foregoing description of the method of the present invention, it is believed that it will be readily apparent that a novel and highly useful method for drilling parallel holes or canals in the teeth is proposed by the invention. The method offers relatively little discomfort to the patient and constitutes a substantial improvement in this particular respect as compared to many of the complicated devices and techniques which have heretofore been in use. The materials and equipment required for practicing the process are relatively inexpensive and simple in construction, and an extremely high degree of technical skill is not required to practice the method. One of the most notable advantages of the invention is the extreme accuracy of parallelism which can be obtained in the practice of the method.

An ancillary, yet novel, aspect of the present invention also resides in the apparatus used for practicing the process of the invention. It is believed that the spotting assembly depicted in full in FIGURE 1 possesses certain novel structure, particularly insofar as such structure is adapted to use in the paralleling procedure hereinbefore described. Further than this structure, the instrument shown in FIGURE 1 is also adaptable for use in the procedure of dental surveying. In surveying, a marking device is used to mark around the lateral or peripheral contours of the teeth for the purpose of establishing the high points or undercuts on the sides of the teeth which can be used as anchor points for bridges, crowns and the like. By inverting the spotting tool 30 so as to bring the end carrying the groove 36 to the lower side of the sleeve 28, a pencil lead 38 or similar marking device may be placed in the groove and used in the surveying technique.

Although a preferred mode of practicing the paralleling process of the invention has been described in the foregoing specification, and likewise, a preferred form of the instrument used in practicing the process has been described and depicted, it can be readily appreciated that many modifications and variations may be made in the described embodiments of the invention without departure from the basic principles which underlie the invention. Insofar, therefore, as these principles are still employed in a paralleling process and in the design of equipment for use therein, such process and equipment are considered to be circumscribed by the spirit and scope of this invention except as the same may be necessarily limited by the appended claims or reasonable equivalents thereof.

What is claimed is: 1. A process for drilling parallel holes in a dentition which comprises the steps of:

making a model of the portion of said dentition in which said holes are to be drilled; establishing the direction of a drilling axis with a guide member; adhering a first guide means to said model at a desired drilling point while maintaining said guide means parallelto said drilling axis with said guide member; adhering a second guide means to said, model ataseca ond desired drilling point while maintaining said second guide means parallel to said first guide means with said guide member; t forming a jig complementary in configuration to the portion of said model to which said first and said second guide means are adhered and containing embedded therein said first and second guide means. removing the jig from the model with the guide means contained therein; fitting said jig over the dentition with said guide means aligned over the portion of said dentition at which it is desired to drill holes; and passing a drilling tool through each of said guide means and drilling said holes while said drilling tool is guided and aligned by said guide means. 2. A process for forming parallel holes in a dentition comprising the steps of:

making a model of the portion of the dentition in which holes are to be drilled, the model being substantially identical in size and configuration to said portion of the dentition; aligning a guide member with the projected axis of the first of said holes at a point on the model corresponding to the point on the dentition at which said first hole is to be formed; adhering a first guide means to said model while said guide means is coaxially aligned with the previously aligned guide member; removing the guide member from alignment with the adhered guide means and positioning said guide member over said model at the point where a second hole is to be drilled, the movement of said guide member being carried out while maintaining the axis of said guide member in parallelism with the projected axis of said first hole and the axis of the adhered guide means; adhering a second guide means to said model while said second guide means is coaxially aligned with the guide member and the projected axis of said second hole; forming a jig including said first and said second guide means with said guide means maintained in parallel- 1sm; removing the jig from the model with the guide means contained therein; positioning the jig with respect to said dentition such that the parallel first and second guide means are positioned over the portion of said dentition wherein the holes are to be formed; and passing a drilling tool through each of said guide means to drill the first and second holes while the drilling tool is guided and aligned by said guide means. 3. A process for drilling parallel holes in teeth while 10 said teeth are in the natural position in the mouth comprising:

making a rigid model of the portion of said teeth in which said holes are to be drilled, said model being substantially identical in size and configuration to said portion of said teeth;

aligning a straight, elongated, rigid guide member with a point on said model corresponding to the point on said teeth at which one of said holes is to be drilled, said guide member being aligned with its longitudinal axis coincident with the projected axis of said one hole;

placing a first generally tubular guide sleeve over said elongated, rigid guide member so that said first sleeve contacts said model while coaxially aligned with said projected axis;

adhering said first tubular guide sleeve to said model While said first tubular guide sleeve is coaxially aligned with said projected axis and in contact with said model;

Withdrawing said rigid guide member from said first tubular guide sleeve and moving said rigid guide member into contact with said model at a point where a second of said holes is to be drilled, the movement of said guide member being carried out While maintaining the axis of said guide member in parallelism with the projected axis of said one hole and the axis of said first generally tubular guide sleeve;

placing a second generally tubular guide sleeve over said elongated, rigid guide member so that said second tubular guide sleeve contacts said model while coaxially aligned with the projected axis of said second hole;

adhering said second tubular guide sleeve to said model while said second tubular guide sleeve is coia;xially aligned with the projected axis of said second 1 ole;

forming a jig complementary in configuration to the portion of said model to which said first and second tubular guide sleeves are adhered and containing embedded therein said first and second tubular guide sleeves with said guide sleeves maintained in parallelism and passing through said jig from one side thereof to the other;

removing the jig from the model with the guide sleeves contained therein to sever the guide sleeves rfrom said model;

fitting said jig over the teeth in the mouth with said tubular guide sleeves contacting the teeth at the points where it is desired to drill said first and second holes; and

passing an elongated drilling tool through each of said tubular guide sleeves and drilling said first and second holes while said drilling tool is guided and aligned by said tubular guide sleeves.

4. The process claimed in claim 3 wherein said jig is formed by covering with an amorphous, easily molded material which can be cured to a hardened, rigid state, the portion of said model to which said first and second tubular guide sleeves are adhered, and simultaneously, surrounding said first and second guide sleeves with said easily molded material while said guide sleeves are adhered to said model.

5. The process claimed in claim 4 and further characterized to include the step of coating said model with a releasing compound prior to forming said jig whereby said amorphous, easily molded material will be more easily released from said model after it has cured to a hardened, rigid state.

6. A dental instrument for use in preparing drill jigs comprising:

a horizontal stage;

a plate slidably supported on the upper horizontal surface of said stage and freely movable in all directions in a horizontal plane;

deformable supporting means on said plate for supporting a model of the teeth of a patient in any desired orientation relative to a horizontal plane and retaining said model in said orientation as said plate is moved on said stage;

a rigid, vertical post extending upwardly from said stage;

a rigid, horizontal arm having first and second ends and slidably and rotatably secured at one of its ends to said post for vertical sliding movement and rotative movement on said post;

a sleeve secured to the other end of said arm and having a bore extending therethrough;

an elongated spotting tool extending through said bore and slidable therein, said elongated spotting tool fitting relatively snugly into said bore for constant extension at the same angle relative to the vertical as said bore;

a spotting mandrel on the lower end of said spotting tool; and

an elongated, generally tubular guide sleeve slidably positioned on said spotting mandrel, said sleeve fitting relatively snugly onto said spotting mandrel whereby the longitudinal axis of said sleeve coincides with the longitudinal axis of said spotting tool.

7. A dental instrument as claimed in claim 6 and further characterized to include means for fixing the rotational and vertical position of said horizontal arm on said vertical post.

References Cited by the Examiner OTHER REFERENCES A Modification of the Pinledge Inlay Technique, by F. E. Pinto in the November 1945 issue of Dental Digest on pages 617-619.

RICHARD A. GAUDET, Primary Examiner.

JAMES W. HINEY, 111., Assistant Examiner. 

1. A PROCESS FOR DRILLING PARALLEL HOLES IN A DENTITION WHICH COMPRISES THE STEPS OF: MAKING A MODEL OF THE PORTION OF SAID DENTITION IN WHICH SAID HOLES ARE TO BE DRILLED; ESTABLISHING THE DIRECTION OF A DRILLING AXIS WITH A GUIDE MEMBER; ADHERING A FRIST GUIDE MEANS TO SAID MODEL AT A DESIRED DRILLING POINT WHILE MAINTAINING SAID GUIDE MEANS PARALLEL TO SAID DRILLING AXIS WITH SAID GUIDE MEMBER; ADHERING A SECOND GUIDE MEANS TO SAID MODEL AT A SECOND DESIRED DRILLING POINT WHILE MAINTAINING SAID SECOND GUIDE MEANS PARALLEL TO SAID FIRST GUIDE MEANS WITH SAID GUIDE MEMBER; FORMING A JIG COMPLEMENTARY IN CONFIGURATION TO THE PORTION OF SAID MODEL TO WHICH SAID FIRST AND SAID SECOND GUIDE MEANS ARE ADHERED AND CONTAINING EMBEDDED THEREIN SAID FIRST AND SECOND GUIDE MEANS, REMOVING THE JIG FROM THE MODEL WITH THE GUIDE MEANS CONTAINED THEREIN; FITTING SAID JIG OVER THE DENTITION WITH SAID GUIDE MEANS ALIGNED OVER THE PORTION OF SAID DENTITION AT WHICH IT IS DESIRED TO DRILL HOLES; AND PASSING A DRILLING TOOL THROUGH EACH OF SAID GUIDE MEANS AND DRILLING SAID HOLES WHILE SAID DRILLING TOOL IS GUIDED AND ALIGNED BY SAID GUIDE MEANS. 